1. Field of the Invention
The present invention relates to a high molecular weight catalyst for producing ketazines, a method for producing the high molecular weight catalyst and a method for producing ketazines comprising reacting ketimines with molecular oxygen using the catalyst.
2. Description of the Prior Art
Ketazines are generally produced by reacting ketones and hydrazine. The drawback of this process is the use of expensive hydrazine. The present invention relates to a method for producing ketazines, such as benzophenone azine, (C.sub.6 H.sub.5).sub.2 C.dbd.N--N.dbd.C(C.sub.6 H.sub.5).sub.2, by oxidation of ketimines, such as diphenylmethane imine, (C.sub.6 H.sub.5).sub.2 C.dbd.NH, without using such hydrazine.
A ketimine, e.g., diphenylmethane imine, is easily produced by the gas-phase reaction of benzophenone [(C.sub.6 H.sub.5).sub.2 C.dbd.O] and ammonia (NH.sub.3) in the presence of thoria (ThO.sub.2) or thoria-silica (ThO.sub.2 -SiO.sub.2), or by the liquid-phase reaction of benzophenone and ammonia, at atmospheric pressure or under an ammonia pressure, in the presence of zinc chloride (ZnCl.sub.2) or ammonium chloride (NH.sub.4 Cl). A method for producing benzophenone azine from diphenylmethane imine and molecular oxygen in the presence of copper (I) chloride, CuCl, is disclosed in U.S. Pat. No. 2,870,206. Another method for producing benzophenone azine by contacting benzophenone in the presence of copper (I) chloride and either of zinc chloride and ammonium chloride with a mixed gas of ammonia and oxygen at atmospheric pressure is disclosed in Chemistry Letters, 1974, pp. 89-90 and 1097-1098, by Hiromu Hayashi et al, or under increased pressure is disclosed in Industrial Engineering Chemistry, Product Research and Development, Vol. 15, No. 4, 229 - 303 (1976), by Hiromu Hayashi et al.
In these processes, the reaction is carried out in a homogeneous liquid-phase system so that complicated processes are required for the separation, recovery and circulation of the expensive catalyst. This causes various problems, for example, an increase in equipment cost or energy cost and the use of special solvents, which become difficulties from an industrial standpoint.
An explanation of these difficulties in the prior art is given in more detail below with reference to a typical example, the production of benzophenone azine.
The formation of benzophenone azine from diphenylmethane imine is shown by the following equation (1). EQU 2(C.sub.6 H.sub.5).sub.2 C.dbd.NH + 1/2O.sub.2 .fwdarw. (C.sub.6 H.sub.5).sub.2 C.dbd.N--N.dbd.C(C.sub.6 H.sub.5).sub.2 + H.sub.2 O (1)
the formed benzophenone azine produces hydrazine and benzophenone according to equation (2) and the benzophenone can be used for the production of diphenylmethane imine by reaction with ammonia according to equation (3), and the resulting imine can be used repeatedly as a material for reaction (1). EQU (C.sub.6 H.sub.5).sub.2 C.dbd.N--N.dbd.C(C.sub.6 H.sub.5).sub.2 + 2H.sub.2 O .sup.acid catalyst 2(C.sub.6 H.sub.5).sub.2 C.dbd.O + N.sub.2 H.sub.4 ( 2) EQU (c.sub.6 h.sub.5).sub.2 c.dbd.o + nh.sub.3 .fwdarw. (c.sub.6 h.sub.5).sub.2 c.dbd.nh + h.sub.2 o (3)
further in the prior art, copper (I) chloride is used as a catalyst in reaction (1). Nippon Kagaku Kaishi, 1973, pp. 1949-1953 discloses that copper (I) chloride and diphenylmethane imine form a 1:1 complex, CuCl.(C.sub.6 H.sub.5).sub.2 C.dbd.NH, and that this complex is converted to benzophenone azine through an oxygen containing copper (II)-imine complex which results from the above 1:1 complex by the absorption of a quarter of a mole of oxygen. Further, Nippon Kagaku Kaishi, 1975, pp. 242-245 discloses that a temperature higher than 120.degree. C should be applied for the formation of benzophenone azine by dehydrogenation of diphenylmethane imine which is a ligand of the oxygen containing copper (II)-imine complex. Still further, it is well known that benzophenone azine can be obtained even at room temperature when pyridine is used as a solvent (as disclosed in U.S. Pat. No. 2,870,206), and this means that the reaction temperature of reaction (1) can be decreased to a large extent. However, when reaction (1) is carried out in a pyridine solvent, various difficulties are encountered. For example, the separation of the catalyst becomes extremely difficult, and, in addition, contamination of the material for reaction (1) with benzophenone cannot be avoided, since benzophenone and diphenylmethane imine have boiling points very close to each other. Accordingly, benzophenone accumulates in the pyridine, which makes a continuous production of the azine impossible.